Referring to FIG. 1, a massage device assembled at a chair or an inner part of a pad for massaging the back of a user is illustrated. To massage the whole back side, the massage device must move reciprocally by being driven by a driving device 2 (referring to FIG. 2). In this example, a driving device 2 of a bi-directional screw rod is used for description. The driving device 2 has a driven seat 21 and a single axial level form roller sets P at a lateral side thereof. When the roller sets P are carried by the driven seat 21 to move reciprocally, the back of the user is massaged.
However, in the prior art, the roller sets P have respective sliding heads 22. The roller sets P move along a smooth path with two ends of the path having respective taper sections 23. The taper sections 23 are used to suit the waist and cervical vertebra portions of the user. In that prior art, as shown in the figures, the taper sections are protruding slopes and the roller sets P return as the sliding heads 22 reach the high place of the taper sections 23.
In fact, the roller sets P returns before the sliding heads 22 reach the highest points of the taper sections 23 for preventing other elements to be damaged or buckled.
From the shape of human body, it is appreciated that human's waist and cervical vertebra has stream line shapes, but the prior art design is not matched to the ergonomics so that the user will feel uncomfortable. Especially the taper section 23 will cause the user to feel ache in the cervical vertebra portion and the back side of the user's head does not be massaged.
For these reasons, many prior arts does not design the taper sections 23 in their massage device, but this still remains the problem unsolved. Thus the prior art design can not make the users feel easy and the massage device can not function satisfactory.